For weeks, pharmacists around the United States have been struggling to fill prescriptions for Adderall, and on Wednesday, the Food and Drug Administration confirmed the nationwide shortage.

“There is not sufficient supply to continue to meet US market demand,” the agency said in a statement.

In August, over 60 percent of pharmacists had trouble getting Adderall, which can treat ADHD, according to a survey from the National Community Pharmacists Association.

Most of the challenges are attributed to manufacturing problems at the pharmaceutical company Teva, which produces more of the stimulant medication than any other company in the US. The company said in August that it was having delays because of labor shortages. Other companies that make generic Adderall also have had the drug on backorder since the end of the summer.

Demand for the drug is also at an all-time high. “The supply that we are manufacturing/distributing right now is on pace to be consistent — or greater than — our supply at this time last year by the end of this year. The demand is not,” an unnamed Teva spokesperson told ABC News.

Adderall prescriptions have been steadily increasing over the past decade. Over the course of the COVID-19 pandemic, there was a significant uptick in prescriptions for people between 22 and 44, according to an analysis from healthcare analytics company Trilliant Health.

There are more prescriptions in that age bracket than ADHD diagnoses, according to the analysis. That might be in part because people could get Adderall prescriptions through direct-to-consumer telehealth startups, which popped up to take advantage of relaxed rules around controlled substance prescriptions during the pandemic. Some of the startups, like Cerebral and Done, are under investigation by federal agencies over their prescribing practices.

The FDA expects most dosages of Teva’s generic Adderall to be on backorder until March.